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@article{IVM_1968_1_a10, author = {L. N. Krivonosov}, title = {Principal nets of parallel and normal correspondence of surfaces in $E_4$}, journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika}, pages = {81--91}, publisher = {mathdoc}, number = {1}, year = {1968}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/IVM_1968_1_a10/} }
L. N. Krivonosov. Principal nets of parallel and normal correspondence of surfaces in $E_4$. Izvestiâ vysših učebnyh zavedenij. Matematika, no. 1 (1968), pp. 81-91. http://geodesic.mathdoc.fr/item/IVM_1968_1_a10/